342 Structure of the Fossil Saurians. 



hollow, but become solid and fill out with age. They usually 

 possess two edges, which are serrated, and united in a sharp 

 point. Teeth of this creature were also found with the edge 

 worn smooth ; these are similar to the canine teeth, or lateral 

 incisor teeth, of the Tapir, or other animals with short canine 

 teeth. The formation of the teeth appears to have proceeded 

 laterally. When the new tooth was sufficiently developed, it 

 forced the old one out, and took its place. Of the jaws or 

 the skull no part has yet been found.* A horn, however, 

 similar in form to the smaller horn of the Rhinoceros, but 

 without being connected by a bony attachment like the horns 

 in the Mammalia, is referred to this Saurus. This part is 

 analogous to the horn, or protuberance, of the Iguana of St. 

 Domingo. The vertebrae which are believed to belong to 

 this animal are furnished with strong and stout processes : 

 the one surface is almost flat, the other somewhat depressed ; 

 both are indistinctly quadrangular. A sacral vertebra re- 

 sembles the first sacral of the Monitor, except that both sur- 

 faces are somewhat concave ; an inferior spinous process, or 

 chevron bone, and a clavicle, more nearly resemble these 

 bones in the living Iguana than in the fossil Megalosaurus. 

 The limbs of this animal were of enormous size: the animal 

 itself must have been colossal. The bones subsequently found 

 in the Isle of Wight satisfactorily confirm these suppositions. 

 A metacarpal bone is twice as broad as that of the Elephant, 

 being 6 in. long, and weighing 6 lb. f 



C. Saurians with Limbs adapted for swimming. 



1, Ichthyosau'rus Konig. 



The head most resembles that of the Lacertae. The beak, 

 however, is elongated, and is almost wholly formed of the 

 intermaxillary bones. The nasal orifices are placed, not as 

 in the Gavial at the point of the beak, but at its commence- 

 ment. The mechanism of hearing was simple and similar to 

 that of the Salamander, Sirene, and Proteus. The most 

 striking features are the enormous eyes, the sclerotica of 

 which was strengthened by a circle of bony plates. This 

 arrangement is more perfect in the Lacertae than in the Birds. 

 The disposition of the different bones of the lower jaw ap- 

 proaches partly to that of the Lacertae, partly to that of the 



* A fragment of the jaw, with rudiments of several teeth, has lately been 

 discovered by Dr. Mantell, and confirms his opinion as to the analogy of 

 the dentation of the Iguanodon with that of the Iguana. — Ed. 



f It is evident that the learned author had not seen Dr. MantelFs last 

 work, the Geology of the South-East of England, in which many new and 

 important facts, relating to the osteology of the Iguanodon, are stated. 

 — Ed. 



